1. Field of the Invention
The present invention relates to a transceiver switchover arrangement, in particular to a two-band transceiver switchover arrangement for the alternating connection of at least one first receiver apparatus and one second receiver apparatus and at least one first transmitter apparatus and one second transmitter apparatus with a single signal coupling/decoupling means, in particular an antenna. The first receiver apparatus and the first transmitter apparatus are designed for a first frequency band f1, and the second receiver apparatus and the second transmitter apparatus are designed for a second frequency band f2, with f2.apprxeq.2*f1.
2. Description of the Prior Art
Circuit arrangements of this sort are required, for example, in many telecommunication systems in order to connect a receiving apparatus with the antenna--or with another signal coupling/decoupling means--in the reception mode, and to connect a transmitter apparatus with the antenna--or with another signal coupling/decoupling means--in the transmitting mode. In particular, this type of circuit arrangement is employed with mobile transceiver apparatuses, which must satisfy two different systems, e.g. GSM and PCN.
From U.S. Pat. No. 5,193,218, a transceiver apparatus is known that employs a switch that connects both the transmitter and the receiver to a common antenna via quarter-wave lines. In addition, from U.S. Pat. No. 5,513,382 such a circuit is known for a radiotelephone that connects, in alternating fashion, a transmitter circuit or a receiver circuit with a common antenna by means of two diodes and a quarter-wave line.
The transceiver switchover arrangements must fulfill the following requirements:
low insertion loss in the switched-on state PA1 high insulation in the switched-off state PA1 high signal-harmonics ratio PA1 high intermodulation resistance PA1 low current consumption; no current consumption, as far as possible, in the reception mode. PA1 a) In the operating mode "Transmission in the first frequency band f1," the first and the fifth on-off switching apparatus are in the on state and the remaining on-off switching apparatuses are in the off state. The series circuit of the two line sections is thus applied to the fixed potential, preferably to ground, via the fifth on-off switching means. Since the series circuit of the two line sections represents a quarter-wave line for the first frequency band f1, the short-circuit to the fixed potential is transformed into a no-load at the terminal for the signal on-off means. Accordingly, in this operating mode, only the first transmitting direction is effectively connected with the signal coupling/decoupling means. PA1 b) In the operating mode "Transmission in the second frequency band f2," the second and the third on-off switching apparatuses are in the on state, and the remaining on-off switching apparatuses are in the off state. The first line section is applied to the fixed potential, preferably to ground, via the third on-off switching apparatus. Since the first line section represents a quarter-wave line for the second frequency band f2, the short circuit to the fixed potential is transformed into a no-load at the terminal for the signal coupling/decoupling means. Accordingly, in this operating mode only the second transmitting apparatus is effectively connected with the signal coupling/decoupling means. PA1 c) In the operating mode "Reception in the first frequency band f1," all the on-off switching apparatuses are in the off state. The terminal for the signal coupling/decoupling means is connected, in accordance with the characteristic impedance, with the first transmitting apparatus for the first frequency band f1, via the first and second line section, which are connected in series. The rest of the circuit arrangement is disconnected. PA1 d) In the last of the four possible operating modes, "Reception in the second frequency band f2," the fourth and the fifth on-off switching apparatus are in the on state, and the remaining on-off switching apparatuses are in the off state. The second receiver apparatus is thus connected, in accordance with the characteristic impedance, with the terminal for the signal coupling/decoupling means, via the first line section. The second line section is in turn applied to the fixed potential, preferably to ground, via the fifth on-off switching apparatus. Since the second line section for the second frequency band f2 represents a quarter-wave line, the short-circuit to the fixed potential is transformed into a no-load at the terminal for the second receive apparatus. Accordingly, in this operating mode only the second receiver apparatus is effectively connected to the signal coupling/decoupling means.